CLEVELAND (AP) — Five years ago, LeBron James left the floor after Game 5 against Boston in disgrace. There were boos from the home fans, even some whispers he'd quit on the Cavaliers.

On Sunday, in his first playoff game for Cleveland since 2010, James will take his first step toward an NBA championship — toward the one that could top them all.

James and the Cavaliers open the playoffs against the Celtics, a team he knows well and the one that abruptly ended his first stay in Cleveland. Shortly before his exit to Miami in the summer of '10, the Cavs were beaten in six games by the Celtics, and that series loss, perhaps as much as any other, scarred James.

"It stuck with me a lot," he said after Friday's practice.

This opening-round matchup appears to be a mismatch for James and the Cavs, who righted themselves after a 19-20 start and are expected to easily dispatch the up-and-coming Celtics. In James, Kyrie Irving and Kevin Love, Cleveland has an updated version of the "Big 3," while Boston traded star guard Rajon Rondo and finished two games under .500.

The oddsmakers have tabbed the Cavs co-favorites to win the title, but James knows well that there are no guarantees.

"Everyone's 0-0 when you get to this point, so our whole game plan right now is giving ourselves a chance to win the game," said James, who has never lost a first-round series.

Since that defeat by Boston in 2010, James has won two titles in Miami, and he's now hoping to quench a 51-year championship drought in a tortured city that didn't take long to re-embrace him.

Cleveland and Boston split the season series, with the Celtics winning twice last week — games in which Cavs coach David Blatt rested starters to be fresh for the postseason.

The only time both teams were at close to full strength was March 3, when the Cavs demolished the Celtics 110-79.

Boston guard Evan Turner knows for the Celtics to have any chance, James must be slowed.

"You try to make it uncomfortable for him, make him work (defensively), contest his shots," Turner said. "I know he's going to get calls, and I know he's going to make a lot of great plays."

There are some other sub-plots to the Celtics-Cavs series:

SMOOTH TRANSITION: Celtics coach Brad Stevens knows his way around the NCAA Tournament, but this is his first dance with the big boys. In 2010 and 2011, he guided Butler to consecutive NCAA title games. He took over the Celtics last season, when they went 25-57 while rebuilding.

PLAYOFF ROOKIES: Irving will make his playoff debut, a game he has dreamed of since childhood.

"This probably will be the biggest game I've played in," said Irving, who in his fourth season has developed into one of the game's elite point guards.

Irving said James has given him some pointers about what to expect in the playoffs, with "preparation" the biggest piece of advice.

Love, too, is a playoff rookie after six seasons in Minnesota. After some early resistance, he's willingly sacrificed personal stats for team goals.

"You can shoot 0 for 35. As long as you win, that's all that matters," Love said.

BIG DIFFERENCE: Boston's trade with Phoenix for 5-foot-9 guard Isaiah Thomas on Feb. 19 changed the season. The Celtics were 20-31 before the deal, 20-11 afterward. Thomas sat out 10 of those games, but Boston was 14-7 when he played, and he led them with 19 points per game.

GREAT EXPECTATIONS: Since James and Love came to town, Cleveland has been tagged as the team to beat. Blatt has spent the season trying to manage the hype.

"It's not sensible and it's not correct to put the cart before the horse," said Blatt, another playoff first-timer. "We've got a lot of tough basketball ahead of us to get anywhere. That's why I think it's a little unfair for people to start claiming that we should do this and do that.

"We haven't done anything as a team yet at this stage."

___

AP Sports Writer Howard Ulman in Boston contributed to this report.